Melissa Etheridge's ExFiles for Custody

7/8/2010 7:50 PM PDT

Melissa Etheridge's Ex Files for Custody

Melissa Etheridge's former domestic partner, Tammy Lynn Michaels, has filed legal docs asking for full custody of their twin children.

TMZ broke the story ... Melissa filed for dissolution of their domestic partnership. In Melissa's docs, she filed for joint legal and physical custody.

But now, Tammy has thrown down the gauntlet, asking for full legal and physical custody. Tammy carried the twins to term, after being impregnated by an anonymous sperm donor.

Tammy, just like Melissa, says in her docs irreconcilable differences as the reason to end their partnership.

Tammy is also asking for spousal support.

Last thing ... it looks like Tammy made a mistake. She filed a dissolution of marriage rather than a dissolution of domestic partnership. The two did not qualify to marry during the time that they established their union.